First off, were the white guys the aggressors?
Watch them being surrounded in this video...
https://www.youtube.com/watch?v=Hc3c6cK9p_w
Second was there reason for the white guys to feel threatened?
Watch these guys describe the black crowd assaulting the white guys...
https://www.youtube.com/watch?v=w3-XIGJZMEI
Finally at the front of this video you can see who surrounded who...
https://www.youtube.com/watch?v=w3-XIGJZMEI
I got URL wrong on that last video, too lazy to refind it. Just showed the crowd surrounding the white fellows in it before the shooting (before they even ran for their lives after being hit).